In connection with vehicles which include an internal-combustion engine, different methods are presently used for treatment of the gas that is being fed from the engine of the vehicle in connection with the combustion which takes place in the engine. Such exhaust treatment then takes place for different reasons, e.g. demands regarding the cleaning of hazardous pollutants in the exhaust gases, as well as desires for greater fuel economy and a longer engine lifetime.
In this context, it is known to use apparatus for ventilating crankcase gases from the crankcase of the engine. The crankcase gases are generated in the various combustion chambers of the engine during operation thereof, and generally contain a relatively high concentration of combustible hydrocarbons. The crankcase gases are directed from the combustion chamber, between the respective cylinder liner and piston ring at the respective engine cylinder, and then to the engine's crankcase. After that, the crankcase gases are led from the crankcase and then on to the engine's oil pan.
According to a known technique, the crankcase gases are fed from the engine's oil pan and back to a suitable point in the engine's inlet side. From there, the gas can once again be sucked into the engine's air inlet for combustion in the engine. The ventilation and return of the crankcase gases back to the inlet side of the engine can reduce the discharge of hazardous pollutants from the engine.
One problem which occurs in known systems of the above type is based upon the fact that the crankcase gases that reach the oil pan flows towards the lubricating oil present in the oil pan. This results in part of the lubricating oil being transformed into an aerosol. If this aerosol should be allowed to be recirculated to the engine's inlet, coatings can be formed on different parts on the inlet side of the engine, e.g. in the combustion chamber of the engine and on the valves.
One further problem is that the aforementioned aerosol contains substances which one would want to separate from the crankcase gases, so that they will not be recirculated to the engine inlet.
In British Patent No. 1481037, apparatus is described for ventilation of crankcase gases in an internal-combustion engine. According to this patent, the crankcase gases, which contain combustible gaseous components, are fed to the engine inlet through an oxidation catalyst. In this oxidation catalyst the combustible gaseous components are oxidized, whereby resulting carbon dioxide and water are recirculated towards the engine inlet. In order to make the oxidation catalyst rapidly reach its correct operating temperature, it is also arranged in mechanical contact with the exhaust manifold of the engine.
Diesel engines for trucks are often designed for turbo charging, whereby an increased amount of air can be compressed and fed into the engine in a well-known manner. Normally, such systems also include an intercooler, whereby the air that is being fed through the compressor can be cooled.
In the engine arrangements that comprise turbo charging and an intercooler, a problem occurs if ventilated crankcase gases are fed to a compressor in the turbo unit, to be compressed and then fed to the intercooler. In this type of apparatus, a high degree of overcharging results in the temperature in the compressor being very high, up to about 170.degree. C. This causes the oil residues in the crankcase gas that are being fed to the compressor to carbonise, which creates a coating in the compressor. This makes the blades in the compressor thicker, which leads to a reduced efficiency of the compressor. To obtain the performance of the engine corresponding to a system without recirculated crankcase gases there would then be a demand for a more efficient intercooler.
A further disadvantage in this arrangement relates to the fact that an oil film is condensed and will form a coating in the bottom of the intercooler. This leads to reduced efficiency of the intercooler. Furthermore, there is a risk that the oil film will be sucked into the engine.
An object of the present invention is to provide an improved apparatus for ventilation of crankcase gases in an internal-combustion engine, and particularly for an internal-combustion engine comprising a turbo unit and an intercooler.